Endometriosis surgery is considered often to be complicated
operations. We therefore wanted to study the rate of complications in
surgery for endometriosis compared to similar surgical intervention
on other indications. The study was performed as a retrospective
case-control study in a university hospital with secondary and
tertiary medical service. 200 women with endometriosis having been
operated between 2000 and 2008 were matched with 400 controls
having similar operations on other benign indications in the same
period of time and being operated by the same staff in the hospital.
Women identified with the ICD-10 diagnosis of endometriosis were
found in the database at the gynecological department and matched
with similar operative procedures performed on patients without
endometriosis. Demographic data, surgical methods and surgical
complications within 60 days were registered. Main outcome were
rate of per- and postoperative complications.

Repeated surgeries, adhesiolysis, a longer operation time, bleeding
and wound infection were significantly more common in endometriosis
surgery than in controls. However, there was no significant difference
in rate of severe and total complications between the endometriosis
and the control group (8.0% versus 6.3% and 28.0% versus 25.8%).
The study indicates that there in our department is no greater risk
of complications in operations performed for endometriosis than for
similar operations for other benign diseases.

Endometriosis is a chronic disease, prevalent in 6-10% of
women of reproductive age [1], where endometrial-like tissue
is placed outside the uterus causing an inflammatory reaction.
There is little correlation between the extent of the disease
and the symptoms. Affected women may experience symptoms
like pelvic pain, infertility and dyspareunia, but can also be
asymptomatic [2]. Other symptoms are dysmenorrhoea, dysuria,
pain at defecation, fatigue and nausea [2]. Laparoscopy is the
gold standard for diagnosing endometriosis [2]. Endometriosis
can be treated surgically or medically. The goal of the treatment
is pain relief and improving fertility. The choice of treatment is individualized with respect to age, symptoms and family planning.
Surgical treatment is preferably performed in connection with
the diagnostic procedure. Repeated surgery is common [3], often
alternated with hormonal treatment. Previous investigations
concerning the results of surgery have focused on certain
manifestations such as ovarian, peritoneal or deep infiltrating
endometriosis, laparoscopic operations or results obtained by a
single surgeon [4-7].

Surgical treatment includes removal of endometriotic
deposits with excision or ablation and removal of adhesions. A
Cochrane review [8] concludes that laparoscopic treatment has a
significantly better outcome on symptoms than mere diagnostic
laparoscopy but there is no current agreement on what surgical
treatment is preferable concerning endometriosis associated
with pelvic pain.

Surgery implies a risk of complications. Surgery for
endometriosis could entail a higher risk because of adhesions
to the bowel and the urinary tract caused by the nature of
the disease, or due to repeated surgery. In recent years The
Norwegian System of Compensation to Patients has received a
considerable number of claims concerning complications after
operations for endometriosis [9]. However, it is unknown if this
reflects a higher rate of operations on this indication or a real
increased risk of surgical complications.

The purpose of this study was to investigate if surgery for
endometriosis entails a higher complication rate compared to the
same surgical procedure performed on other benign indications.

Methods

This is a retrospective case review based on operations
carried out from January 2000 to December 2008 at The
Department of Obstetrics and Gynecology, St. Olavs Hospital,
Trondheim, Norway, a university hospital with secondary and
tertiary service. A total of 200 patients were discharged with the
ICD-10 diagnosis endometriosis, N80.1-N80.9. The patients were
divided into three groups according to the type of surgery: partial
or complete adnexal surgery, uterine surgery with or without adnexal surgery, and peritoneal surgery only. Patients with
adenomyosis or malignancy were excluded. The revised ASRM
classification was used to determine the stage of endometriosis
[10]. The control group consisted of 400 patients, two controls
for each case. These patients had undergone surgery in the same
department during the same period of time. Using the NCMP/
NCSP Classification of Surgical Procedures [11], we matched
patients with controls having had similar type of surgery. The
endometriosis patients with peritoneal surgery were matched
with controls undergoing tubal sterilization as we found this to be
the most comparable intervention, as women in both groups had
laparoscopic cauterization. All patients had undergone surgery
due to a benign indication by the same staff of gynecologists,
irrespective of the diagnosis. In our department the routine is
that trainees are assisted by specialists.

Demography, stage of endometriosis, type of surgery, and perand
postoperative complications within 60 days were registered
from medical records. Severe complications comprised injury to
the urinary tract or intestines and life threatening peroperative
episodes. Information about hospital stay and sick leave was
obtained.

Statistical analyses were carried out using the SPSS software
package, version 16.0. Data were compared using: The Chisquare
test at cross tabulations, The Independent-Samples T-test
for finding means and The Mann-Whitney U-test to compare
two independent groups. We considered p-values < 0.05 as
statistically significant. The sample size of 200 cases and 400
controls was based on power computation calculated by the
software “SamplePower”. As the expected surgical procedures
differed in type, we arbitrarily estimated the intra- and
postoperative complication rate in the control group to be 5%
and in the cases of endometriosis to be 12%. We would then be
able to show a statistical significant difference with a power of
83%.

The study was approved by the Regional Research Ethics
Committee of Central Norway, Norwegian Social Science Data
Services and Privacy Ombudsman for Research.

Results

Patients with endometriosis were significantly younger
than controls group (38.1 years ± 8.4 versus 46.2 years ± 15.6,
p < 0.001). Previous surgery was more common among women
with endometriosis (Table 1). Table 2 shows the stage of
endometriosis according to the ASRM classification [10]. A total
of 85.5% had moderate or severe endometriosis. Table 3 shows
that 58.5% of the patients had open surgery, while 41.5% had
laparoscopic operations only. The equal frequencies refer to
matching. However, it should be mentioned that some patients in
each laparotomy group had had a conversion from laparoscopy
(9.5% with endometriosis versus 7.5% of controls, n.s.). In Table
4 is seen a significant difference between the endometriosis group
and controls concerning operation time (106 min. ~94 min, p =
0.008), need of adhesiolysis (54.5%∼29.5%, p = 0.000) and blood
loss (366ml∼274ml, p = 0.001). However, neither the length of
hospital stay after surgery nor the length of sick leave differed between the two groups. Table 5 shows no significant difference
in the rate of severe and total complications between the two
groups (8.0% versus 6.3% and 28.0% versus 25.8%). Wound
infection was the only complication that occurred significantly
more often in the endometriosis group (5.5%~2.2%, p = 0.04) but
the frequency was low.

Discussions

The main findings of our study were that endometriosis
patients were younger and more often had previous surgery.
Adhesiolysis, longer operation time, greater blood loss and
wound infections were more common in endometriosis surgery.
However, the rate of severe or moderate complications did
not differ significantly from similar surgery for other benign
conditions.

The strength of our study is that the patients and the controls
were operated in the same department by the same staff and
in the same interval of time. We were able to trace all medical
records from the period of investigation. The weakness is the
retrospective design investigating surgery performed during
several years with different surgeons. However, as this is a
comparative study with the controls recruited in the same period,
this effect should be eliminated by matching.

The rate of laparotomy (58.5%) was higher than expected,
but it should be noted that 9.5% in the endometriosis group and
7.5% among the controls were conversions from laparoscopy.
Today the use of laparoscopic surgery probably is higher. Patients
with deep infiltrating endometriosis of the rectovaginal space
were not present in our material as these patients routinely are
referred to a national specialist center for surgery, and in addition
they could not have been matched with controls.

Table 1: Characteristics of the 200 patients operated for endometriosis
and 400 controls concerning age and previous surgery.

Variable

Endometriosis

(n = 200)

Control

(n = 400)

p-value

Age, years (mean ± SD)

38.1 ± 8.4

46.2 ± 15.6

0.00

Previous surgery, n (%)

No

111(55.5)

260(65)

<0.05

Yes

89(44.5)

140(35)

<0.05

1 previous operation

50 (25)

96 (26)

<0.05

≥ 2 previous operations

39 (19.5)

44(11.1)

<0.05

Number of previous surgery, mean ± SD

0.78 ± 1.15

0.56 ± 1.13

0.026

Table 2: Stage of endometriosis in 200 patients according to the ASRM
classification (Revised American Society for Reproductive Medicine
classification of endometriosis) [10].

Stage of endometriosis (n = 200)

I Minimal, n (%)

3 (1.5)

II Mild, n (%)

26 (13)

III Moderate, n (%)

97 (48.5)

IV Severe, n (%)

74 (37)

Table 3: Distribution of 200 patients with endometriosis and 400
matched controls between different procedures and surgical techniques.

* Information obtained from 189 with endometriosis and 384 controls.
** Information obtained from 152 with endometriosis and 350 controls.
*** Based on data from working women, respectively 157 and 215.

* Information obtained from 96 with endometriosis and 185 controls.
** Information obtained from 186 with endometriosis and 374 controls.
*** Three controls had urinary tract as well as intestinal injuries

As endometriosis is a disease mainly affecting women in
reproductive age, it is obvious that the patients had a lower mean
age than controls, with 38 years versus 46 years. This was also
demonstrated in the study of Maytham et al. [6] in operations
for colorectal endometriosis, which showed a much greater
difference with a median age of 33 years in the endometriosis
group and 72 years in the control group. However, the lower
age of patients compared to controls in our material probably
would not influence the result because both groups were mostly
premenopausal women.

In spite of the endometriosis group being eight years
younger, they have had significantly more previous gynecological
operations. This is in accordance with a high recurrence rate
of endometriosis in fertile women [3]. It also confirms that
endometriosis is a chronic recurrent disease.

Most patients in our study group (85.5%) had moderate
or severe endometriosis. This, in addition to a higher rate of
previous surgery, explains the high rate of adhesiolysis. Pelvics
surgery in an area with adhesions is more risky. This might
explain a prolonged operation time of 12 minutes in the study
group as well as a significantly increased blood loss. Blood
transfusion was, however, not more common among patients
with endometriosis. A transfusion rate of 3.0% is comparable to
the rate in the study of Spilsbury et al. [12] where 2.41% of the
patients required blood transfusions.

Overall we found that 28.0% of the patients with
endometriosis had at least one complication, versus 25.8% in the
control group. Because of the lack of similar studies and because
there is no standard definition of complications, we cannot
compare the overall result with other studies.

The total rate of severe complications, including urological
and intestinal injury, was 12% versus 8.3%. It is stated that
adhesions, previous surgery and endometriosis may increase the
risk of bladder injury [13,14]. However, our data do not support
this, since there was no significant difference between the two
groups. Urinary tract injuries occurred equally in the two groups
and the frequencies of 1,5% were comparable to the figures
of 1,1% in a recent study of Rettenmaier et al. [14] . Intestinal
injury occurred in 6.5% of the patients with endometriosis and
in 5.5% of the control patients. This is a higher percentage than
found in the study of Rettenmaier et al. [14]. The explanation for
this may be that we classified minor damage to the serosa as an
intestinal injury. There was no significant difference between
the two groups in the rate of reoperations done within 60 days
after surgery, with four (2.0%) patients in the endometriosis
group and ten (2.5%) patients in the control group. Three of the
reoperations in the endometriosis group were caused by bowel
injury and one by ureter injury. In the control group, bowel injury
caused three of the reoperations and bladder injury caused one.
Two were caused by hematomas and four by minor complications.

Wound infection occurred in 5.5% of the patients with
endometriosis and in 2.2% of the control group. This constitutes
a significant difference, but the reason for this is unclear and
difficult to account for. It may be caused by longer surgery time or greater blood loss. Fever > 38°C was, however, not more
common in the endometriosis group indicating that the infections
were mild.

Postoperative stay in hospital was almost the same in the
two groups, a median of three days. Maytham and co-workers [6]
also presented median post-operative hospital stay of three days.
Both groups were given sick leave for 3-4 weeks on average,
indicating a similar postoperative recovery. 46.3% in the control
group did not work versus 21.5% of the endometriosis group,
reflecting the age difference between the younger patient group
and the older control group.

Conclusion

Our data indicate that there is no greater risk of complications
in operations performed for endometriosis than in similar
operations for other benign diseases despite a higher rate of
repeated surgery and thus the need for adhesiolysis. It is possible
that the considerable experience of our department, being part
of a university hospital offering secondary as well as tertiary
gynecological services, has considerable experience which might
have affected the results. However, we can reassure our patients
that surgery for endometriosis does not have a higher risk of
complications than operations for other conditions.